The present invention is generally related to processor-based control techniques for vehicles, and, more particularly, to system with controller and method for electronically controlling a park-interlock device in a land-based vehicle. More specifically, the present invention allows for utilizing the park-interlock device to control vehicle roll in a vehicle equipped with an electric/hybrid electric or ISG (Integrated Starter Generator) propulsion system requiring implementation of a xe2x80x9cHill-holdxe2x80x9d function during stop/start of the vehicle.
Presently prescribed governmental regulations and/or standards, such as the Federal Motor Vehicle Safety Standards, (FMVSS) require the installation of a parking interlock device to mechanically lock the wheels of the vehicle when parked. Typically, this is accomplished by locking the output shaft of the transmission, thus preventing the vehicle wheels from rotating when the shift selector is placed in the xe2x80x98Parkxe2x80x99 position. One of the purposes of this device is to prevent the vehicle from rolling when parked on a surface with a gradient, i.e., a surface with a slope or inclination. This requirement also applies to electric or hybrid electric vehicles, such as may be equipped with an ISG system. Thus, an interlock park device would be needed as part of the electric power train regardless of whether or not the vehicle is equipped with an automatic transmission.
In known implementations, the interlock device is generally responsive to a shift selector lever that includes Park, Reverse, Neutral, and at least one forward Drive position. The shift lever includes a cable connected to a pawl lever anchored by a pivot pin connected to the transmission case. A toothed pawl gear is mounted on the output shaft of the transmission, and a toggle or plunger, which is spring loaded (e.g., by torsion springs) provides an engagement force with the pawl gear so as to mechanically lock the output shaft connected to the driven wheels of the vehicle. Thus, known park interlocking devices are commonly actuated by a mechanical linkage to the gear shift selector lever, e.g., cable and associated components. The FMVSS prescribes the conditions to which the device must perform. Examples of these conditions include: xe2x80x9cRatchetxe2x80x9d, Hill-hold (tooth abutment condition), and vehicle roll to prescribed lock-up limits. Various values of surface gradients and limiting speeds are prescribed in the FMVSS, and the device must comply with such standards, or any applicable standards.
The shortcomings of known mechanically controlled park interlocking devices, in general, are the difficulties in systematically managing the required shift effort, linkage tolerances, and lack of fault detection as to faults that may develop in the interlocking device. For example, the mechanical linkage between the interlocking device and the shift selector may result in mismatched detent combs, misalignment of the park interlock position and inadequate engagement loads to the park interlock to quickly achieve the appropriate locking functionality. This could ultimately result in inadequate Hill-hold engagement performance (e.g., the vehicle may roll down hill faster than the park interlock can engage) and/or high xe2x80x9cratchet-downxe2x80x9d engagement speed (e.g., if the shift selector is placed in Park while the vehicle is moving above some relatively low speed, e.g., approximately 5.0 mph, the interlock device might engage, and result in bodily injury to the occupants, equipment damage, or both).
Within the field of electric/hybrid electric and ISG propulsion systems, in order to economically and reliably benefit from on demand xe2x80x9cHill-holdxe2x80x9d functionality from the park-interlock device, it would be desirable to provide xe2x80x9cinterlock-by-wirexe2x80x9d, i.e., electronically-based, control techniques and device responsive to electrical signals from a controller, as opposed to a purely mechanically controlled interlock device, that avoids the above-described difficulties. It would be further desirable to provide an interlock device, capable of being directly controlled by the electric/hybrid or ISG controller, including a sensor for detecting malfunctions in the device. It would also be desirable to provide techniques for controlling an interlock park device in an electric, ISG or hybrid electric vehicle in order to utilize the park-interlock device for the purpose of xe2x80x9cHill-holdxe2x80x9d in the stop/start mode of operation without resorting to complex control algorithms, expensive sensors or without having to perform burdensome hardware modifications to the vehicle.
Generally, the present invention fulfills the foregoing needs by providing in one aspect thereof a method for controlling a park-interlock device in a land-based vehicle, such as an electric/hybrid electric or ISG equipped vehicle. The vehicle includes a driver-selectable shifter for selecting a respective one of a plurality of propulsion modes of the vehicle. One of the propulsion modes is a park mode. The method allows for configuring a controller to determine at least one operational mode for stopping and starting a vehicle. The method further allows for sensing at least one vehicle parameter for determining whether or not the park interlock device is to be actuated to a respective interlock state corresponding to the driver-selected mode and/or the controller-determined operational mode. Memory is provided for storing nominal values for each vehicle parameter. A comparing action allows to compare the sensed vehicle parameters relative to the nominal parameter values stored in memory. Based on the results of the comparison, the method allows for generating a control signal for commanding the interlock device to the respective interlock state.
The present invention further fulfills the foregoing needs by providing in another aspect thereof, a method for controlling a park-interlock device in a land-based vehicle. The method provides a driver-selectable shifter for selecting a respective one of a plurality of propulsion modes of the vehicle. The method further allows for providing a controller configured to determine at least one operational mode for stopping and starting the vehicle during a Hill-hold vehicle operation. A storing action allows to store a plurality of park interlock logical rules for determining whether or not the park interlock device should be actuated to a respective interlocking state based, at least in part, on the respective propulsion mode selected by the driver, and/or based on the operational stop/start mode determined by the controller, e.g., an ISG controller. The park interlock rules are processed using at least one vehicle parameter so that based on the actual values of each vehicle parameter relative to a nominal set of vehicle parameter values, a control signal for commanding the interlock device to the respective interlock state is generated.
In one aspect thereof, the present invention provides a system for controlling a park-interlock device in a land-based vehicle. The system includes a driver-selectable shifter for selecting a respective one of a plurality of propulsion modes of the vehicle. A controller is configured to determine at least one operational mode for stopping and starting the vehicle. At least one sensor is provided for sensing at least one vehicle parameter for determining whether or not the park interlock device is to be actuated to a respective interlock state corresponding to the driver-selected mode and/or the controller-determined mode. The system includes a memory for storing nominal values for the vehicle parameters. A comparator is configured to compare each sensed vehicle parameter relative to the values stored in memory so that based on the results of the comparison, a control signal for commanding the interlock device to the respective interlock state is generated by the controller.
In yet another aspect thereof, the present invention provides a controller for controlling a park-interlock device in a land-based vehicle with a driver-selectable shifter for selecting a plurality of propulsion modes of the vehicle. The controller is responsive to at least one sensor for sensing at least one vehicle parameter for determining whether or not the park interlock device is to be actuated to a respective interlock state. The controller includes memory configured to store a plurality of park interlock logical rules for determining whether or not the park interlock device should be actuated to a respective interlocking state based on the respective propulsion mode selected by the driver and/or as determined by the controller while stopping and starting the vehicle in accordance with prescribed vehicle regulations. The memory is further configured for storing nominal values for the vehicle parameters. A comparator is configured to compare each sensed vehicle parameter relative to the nominal values stored in memory so that based on the results of the comparison, a control signal for commanding the interlock device to the respective interlock state is generated by the controller. In one aspect of the invention, the functional state of the park-interlock device is determined or coordinated relative to a Hill-hold function provided during stop/start of a hybrid/electric vehicle equipped with an ISG propulsion system, for example.